Chicken Little

From Conservapedia

Chicken Little is a term used to describe an alarmist who exploits the fears of others by exaggerating the risk of a calamity. Liberals employ this alarmism in an attempt to obfuscate deceit. Such is the case with imaginary global warming.

In children's stories, Chicken Little was a chicken who, because something once fell on his head, runs around insisting that the sky is falling.[1]